Board Thread:Questions and Answers/@comment-96.252.62.116-20171011103947/@comment-96.252.62.139-20181213052053

Well I guess the answer is neither, according to Devil May Cry 5's website it's officialy translated as "Devil Sword Sparda"

https://i.imgur.com/nxf9Itg.png

Though it is confusing that they use "デビル" for the Devil in Devil May Cry ( デビル メイ クライ ) & Devil Trigger (デビルトリガー), but then used "魔剣" for the Devil in Devil Sword Sparda.